# ps -ef | grep sendmail
if sendmail is running, check sendmail.cf and look for
DS=yourmailer@domain.com
This is your relay mail server if you using a relay to send mail else leave it empty for direct sending.
# echo "test" | /usr/lib/sendmail -v id@domain.com
You will see something like this...
220-
220- Unsolicited bulk e-mail is not allowed to transmit,
220- or distribute from our computers and networks.
220-
220 All activities to our networks is now being captured and logged.
>>> EHLO mac.domain.com
250-apple.domain.com Hello mac.domain.com
[x.x.x.x], pleased to meet you
250-ENHANCEDSTATUSCODES
250-8BITMIME
250-SIZE 4000000
250-DSN
250-ONEX
250-XUSR
250-AUTH LOGIN PLAIN
250 HELP
Goodluck